The inventive concepts disclosed herein relate to head up displays (HUDs). More particularly, embodiments of the inventive concepts disclosed herein relate to head up displays (HUDs) for use in small space envelope including but not limited to fixed combiner HUDs for automotive applications.
HUDs provide significant safety and operational benefits including better situational awareness for an operator of equipment, such as, a vehicle. The HUDs can provide instrumentation information into the operator's view of the environment as well as enhance the operator's view of the environment using data from sensors, databases (e.g., maps) or other equipment. Vehicle instrumentation information provided in the operator's field of view of the environment allows the driver of the automobile to view speed, warning lights, and other information without diverting his or her eyes from the environment.
Conventional HUDs are generally relatively large, expensive, and difficult to fit into small space envelopes associated with vehicles. Often, conventional HUDs rely on large optical components to form adequate field of view and viewing eye box. The large optical components are often associated with collimating or non-collimating projectors and include lenses, prisms, mirrors, etc. For example, U.S. Pat. No. 6,359,737 discloses a HUD that uses a conventional projector to display information on a curved windshield used as a combiner. Using a windshield combiner adds to the expense of the projector and can require unique optics for each windshield design. Also, the conventional projector of U.S. Pat. No. 6,359,737 has a large space envelope (which can have a volume of approximately 10 liters) and the windshield/combiner of U.S. Pat. No. 6,359,737 has a small field of view such as 5 degrees.
Substrate guided HUDs have been proposed which use waveguide technology with diffraction gratings to preserve eye box size while reducing size of the HUD. U.S. Pat. No. 4,309,070 issued St. Leger Searle and U.S. Pat. No. 4,711,512 issued to Upatnieks disclose substrate waveguide HUDs. It is desirable to provide HUDs in a compact arrangement suitable for automobile applications.
Therefore, there is a need for compact, low cost HUD systems. Further, there is a need for a compact HUD with a wide field of view. Yet further, there is also a need for a small volume, lightweight, lower cost HUD for vehicle applications. Yet further still, there is a need a HUD that provides virtual images (e.g., enhanced images and mapping images) and instrumentation information to different focal lengths using a waveguide combiner. Still further, there is a need for there is a need a HUD that provides virtual images (enhanced images and mapping images) and instrumentation information to different focal lengths without requiring a large projector.